1. Field of the Invention
The present invention relates to an image processing technique and more specifically a technique of adjusting an interpolated image.
2. Description of the Related Art
In an image display apparatus, adjustment of images are sometimes required to convert given original images into those suitable for an image display section. For example, if the resolution of an original image is greater than the displayable resolution of the image display section, contraction of the original image is required. In a concrete example, when an input original image of SXGA is displayed by the image display section that is capable of displaying images of XGA, the original image is to be contracted.
For contraction of the original image, the original image generally undergoes a skipping process. An interpolating process is often carried out simultaneously with the skipping process. One method applicable for the skipping process selectively skips a group of pixels aligning in either the vertical direction or the horizontal direction (hereinafter referred to as a line image) in an image. One method applicable for the interpolating process carries out interpolation with regard to a line image adjoining to a line image of interest, which is the object of the skipping process. The interpolating process causes information regarding pixels of interest, which are the object of the skipping process, to be left in a resulting image after the skipping process. For example, if one white line image is present in a black image and this white line image is the object of the skipping process, the interpolating process generates a gray line image in the black image, so as to prevent the line information from disappearing from a resulting image.
The resulting image subjected to the selective skipping process and the interpolating process disadvantageously has the deteriorating picture quality. In the above example, the white line image included in the black image is reproduced as a gray line image included in the resulting black image. This does not accurately reproduce the information with regard to the original image.
The object of the present invention is thus to provide a technique that effectively relieves potential deterioration of the picture quality due to an interpolating process carried out simultaneously with a skipping process.
At least part of the above and the other related objects is attained by an image display apparatus, which includes: an image adjustment section that adjusts a given original image; and an image display section that displays the adjusted image. The image adjustment section has: an interpolating process section that, when a skipping rate of the original image is set in at least one of a horizontal direction and a vertical direction, carries out a skipping process at selected positions in the at least one of the horizontal direction and the vertical direction, and simultaneously carries out interpolation on non-skipped pixels adjacent to skipped pixel, thereby generating an interpolated image; and a filtering section that carries out a filtering process on the interpolated image, the filtering process being carried out with a spatial low pass filter and a spatial high pass filter which are used substantially in this sequence.
The image display apparatus has the filtering section, which adjusts the distribution of pixel values in the interpolated image created by the selective skipping process and the interpolating process to a distribution similar to the distribution of pixel values in the original image. This arrangement effectively relieves potential deterioration of the picture quality of the interpolated image.
In accordance with one preferable application of the image display apparatus of the present invention, the filtering process uses one composite image filter which is obtained by combining the spatial low pass filter with the spatial high pass filter.
This arrangement ensures the quick filtering process carried out in the filtering section.
In accordance with one preferable embodiment of the image display apparatus of the present invention, the image adjustment section further includes a contrast compensation section that compensates contrast of a resulting image processed by the filtering section. The filtering section has: a first image filtering section that carries out a filtering process with the spatial low pass filter; and a second image filtering section that carries out a filtering process with the spatial high pass filter. The first image filtering section and the second image filtering section carry out the filtering process with a selected one of a plurality of first filtering coefficients and a selected one of a plurality of second filtering coefficients, respectively, the selected first filtering coefficient and the selected second filtering coefficient being related to each other. The contrast compensation section carrying out the compensating with a selected one of a plurality of contrast compensation values, the selected contrast compensation value being related to the selected first and second filtering coefficients. Available combinations of the selected first and second filtering coefficients and the selected contrast compensation value is determined in advance.
The arrangement of mutually mapping the first filtering coefficient, the second filtering coefficient, and the contrast compensation value to one another facilitates the specification of the filtering processes carried out in the filtering section with the first and the second image filters as well as the processing carried out in the contrast compensation section.
In accordance with another preferable embodiment of the image display apparatus of the present invention, the image adjustment section further includes a contrast compensation section that compensates contrast of a resulting image processed by the filtering section. The filtering section has: a first image filtering section that carries out a filtering process with the spatial low pass filter; and a second image filtering section that carries out a filtering process with the spatial high pass filter. The first image filtering section and the second image filtering section carrying out the filtering process with a selected one of a plurality of first filtering coefficients and a selected one of a plurality of second filtering coefficients, respectively. The contrast compensation section carrying out the compensating with a selected one of a plurality of contrast compensation values. The selected second filtering coefficient and contrast compensation value are related to each other in advance, whereas the first filtering coefficient is selected independently of the second filtering coefficient and the contrast compensation value.
The arrangement of mutually mapping the second filtering coefficient and the contrast compensation value to each other facilitates the specification of the filtering process carried out in the filtering section with the second image filter as well as the processing carried out in the contrast compensation section. Compared with the apparatus of the above configuration, the configuration of independently selecting the first filtering coefficient enables a greater number of different processes to be carried out in the filtering section and the contrast compensation section.
The image display apparatus having any of the above configurations may be a projection display apparatus that displays a projected image. In this case, the interpolating process section carries out the skipping process to correct a keystone distortion of the projected image.
In the case where the image display apparatus is a projection display apparatus, a keystone distortion (that is, a trapezoidal distortion) often arises in the resulting projected image, based on the positional relationship between the projection display apparatus and the screen. The skipping process is generally required to correct such a keystone distortion. The image display apparatus of the present invention effectively relieves potential deterioration of the picture quality due to the skipping and interpolating processes carried out to correct the keystone distortion.
The present invention is also directed to a method of displaying an image, which includes the steps of: adjusting a given original image; and displaying the adjusted image. The step of adjusting the original image includes the steps of: when a skipping rate of the original image is set in at least one of a horizontal direction and a vertical direction, carrying out a skipping process at selected positions in the at least one of the horizontal direction and the vertical direction, and simultaneously carrying out interpolation on non-skipped pixels adjacent to skipped pixels, thereby generating an interpolated image; and carrying out a filtering process on the interpolated image, the filtering process being carried out with a spatial low pass filter and a spatial high pass filter which are used substantially in this sequence.
This method exerts the same functions and advantages as those discussed above with regard to the image display apparatus, and relieves potential deterioration of the picture quality due to the skipping and interpolating processes.
The present invention is further directed to an image processing apparatus, which has an image adjustment section that adjusts a given original image. The image adjustment section includes: an interpolating process section that, when a skipping rate of the original image is set in at least one of a horizontal direction and a vertical direction, carries out a skipping process at selected positions in the at least one of the horizontal direction and the vertical direction, and simultaneously carries out interpolation on non-skipped pixels adjacent to skipped pixel, thereby generating an interpolated image; and a filtering section that carries out a filtering process on the interpolated image, the filtering process being carried out with a spatial low pass filter and a spatial high pass filter which are used substantially in this sequence.
The present invention is also directed to a method of processing an image, which has the step of adjusting a given original image. This step includes the steps of: when a skipping rate of the original image is set in at least one of a horizontal direction and a vertical direction, carrying out a skipping process at selected positions in the at least one of the horizontal direction and the vertical direction, and simultaneously carrying out interpolation on non-skipped pixels adjacent to skipped pixels, thereby generating an interpolated image; and carrying out a filtering process on the interpolated image, the filtering process being carried out with a spatial low pass filter and a spatial high pass filter which are used substantially in this sequence.
The image processing apparatus and the corresponding method exert the same functions and advantages as those discussed above with regard to the image display apparatus and the corresponding method, and relieves potential deterioration of the picture quality due to the skipping and interpolating processes.
The present invention is also directed to a computer program product for processing an image, which includes: a computer readable medium; and a computer program, stored on the computer readable medium, for adjusting a given original image. The computer program has: a program for causing a computer, when a skipping rate of the original image is set in at least one of a horizontal direction and a vertical direction, to carry out a skipping process at selected positions in the at least one of the horizontal direction and the vertical direction, and simultaneously to carry out interpolation on non-skipped pixels adjacent to skipped pixels, thereby generating an interpolated image; and a program for causing the computer to carry out a filtering process on the interpolated image, the filtering process being carried out with a spatial low pass filter and a spatial high pass filter which are used substantially in this sequence.
The computer program product exert the same functions and advantages as those discussed above with regard to the image display apparatus, the image processing apparatus and the corresponding methods, and relieves potential deterioration of the picture quality due to the skipping and interpolating processes.
The technique of the present invention is attained by a variety of applications including an image display apparatus and its corresponding method, an image processing apparatus and its corresponding method, computer programs to attain the functions of these apparatuses and the methods, recording media in which such computer programs are recorded, and data signals that include such computer programs and are embodied in carrier waves.
These and other objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with the accompanying drawings.